In the past few decades, the petroleum industry has invested heavily in the development of marine seismic survey techniques that yield knowledge of subterranean formations beneath a body of water in order to find and extract valuable mineral resources, such as oil and natural gas. High-resolution seismic images of a subterranean formation are essential for quantitative seismic interpretation and improved reservoir monitoring. For a typical marine seismic survey, an exploration-seismology vessel tows a seismic source and one or more streamers just below the surface of the water over a subterranean formation to be investigated for mineral deposits. The vessel contains seismic acquisition equipment, such as navigation control, seismic source control, seismic sensor control, and recording equipment. The seismic source control causes the seismic source, which is typically an air gun, to produce an acoustic impulse at selected times. The impulse sound waves travel down through the water and into the subterranean formation. At each interface between different types of rock, a portion of the sound wave is reflected back toward the surface and into the body of water. The streamers towed behind the vessel are elongated cable-like structures. Each streamer includes a number of sensors that detect pressure and velocity changes in the water created by the sound waves reflected back into the water from the subterranean formation and by the sound waves reflected off of the water surface. The pressure and velocity changes associated with sound waves reflected off of the water surface are referred to as a “surface reflection” that creates a “ghost” signal in seismic signals recorded by the recording equipment. The ghost signal is manifest as spectral notches in the recorded signals that make it difficult to obtain accurate high-resolution seismic images of the subterranean formation.
The ghost signal is influenced by the water surface topography and reflection coefficients. As a result, a number of techniques have been developed to characterize the time-varying water surface topography in an effort to de-ghost recorded signals. However, when water surface images and reflection coefficients do not properly characterize the water surface, the seismic images of subterranean formations produced from de-ghosted signals are still generally inaccurate. In particular, water surface images obtained without taking into account an accurate estimate if the streamer depth can result in an inaccurate vertical position of water surface images, which contributes to inaccuracy of images of the subterranean formation. As a result, those working in the petroleum industry continue to seek systems and methods to more accurately determine the streamer depth.